Description (adapted from the application): The Cell Biology Core has evolved during the first grant period and is focused on two main functions, namely the provision of islets for biological or immunological studies and the provision of a wide variety of cell imaging methodologies for the localization of protein or cells. When the Core was originally proposed, it included a Sub-Core for the production of monoclonal antibodies. However, funding limitations in the first two years of the grant and the decision of HHMI to discontinue support for the production of monoclonal antibodies meant that the DERC would need to totally fund the operation, a situation which was not economically viable. Thus, this Sub-Core has never been operational. The major goal of the Islet Sub-Core is to be a resource for DERC members to facilitate research dealing with islet biology and islet injury by the immune system. These activities require a readily available supply of freshly isolated islets and insulinoma lines as well as facilities to evaluate the functional status of the islets. This Sub-Core provides centralized facilities and services required to efficiency accomplish these tasks. The major goal of the Immunocytochemistry Sub-Core is to facilitate the use of cell imaging techniques in the analysis of tissue distribution and sub-cellular localization of proteins. Immunocytochemical procedures for the localization of proteins in tissues and cells, including conventional light immunomicroscopy, confocal microscopy and electron immunomicroscopy, provide essential information for cell biology, but are not easily accessible to investigators without considerable training and experience. The Sub-Core will make available to the DERC investigators a centralized service for imaging procedures and will provide expertise in the application of these specialized technologies. Through training activities, the Sub-Core will also promote direct access of the individual DERC investigators to the equipment for cell imaging.